User Activity

I am with eBay as a seller for 4 years. eBay used to answer the question I needed quickly but they don't do this anymore. They don't take question or answer via email. They are keep changing the system and getting harder to obtain the answer. I have ...
I am getting same user keep changing the username and i am keep blocking her.Because she has bad reputation and feedback.She purchsed from me once , but since then she changed username three times and has not paid the last item she has won.Now she ca...
I have sent her message and invoice but no reply. Did anyone have same experience? What should I do ?